Parking brakes with which motor vehicles are conventionally equipped are “hand” brakes which comprise a lever connected by a cable to a mechanism for applying two of the brakes of the vehicle.
In order to apply such a parking brake, the driver of a vehicle pulls on the control lever and more or less feels a brake-application force from the resistance to movement of the lever, particularly towards the end of its travel. If the vehicle is parked on a slope and begins to move, that encourages the driver to pull more firmly on the lever in order to apply the brakes more firmly and immobilize the vehicle. It is always incumbent upon the driver of the vehicle to apply the parking brake and to do so correctly.
Certain models of vehicle are currently equipped with automatic parking brakes comprising driven means for applying two of the brakes of the vehicle, these means being operated for example by an electric contactor. Actuation of this contactor on the part of the driver causes two of the brakes of the vehicle to be applied, one on the right and one on the left. If, for any reason, one of these brakes is not correctly applied, the driver has no direct or indirect way of knowing this unless the vehicle is parked on a slope and begins to move. It is therefore necessary to provide a means for monitoring the correct application of motor vehicle automatic parking brakes.
To do this, one conceivable way is to fit strain gauges into a vehicle brake in order to check that this brake has been applied correctly on the strength of the signals supplied by the strain gauges. However, such a solution would be too expensive because of the relatively high cost of strain gauges.